Disc drive data storage devices are well known in the industry. Such devices use rigid discs coated with a magnetizable medium for storage of digital information on a plurality of circular concentric data tracks. The information is written to and read from the discs using a transducer head mounted on an actuator mechanism which moves the head from track to track across the surface of the disc under control of electronic circuitry. The disc or discs are mounted for rotation on a spindle motor which causes the disc to spin at a very high constant speed and the surfaces of the disc to pass under the heads.
As magnetic storage densities have increased, magnetic disc drives have been required to operate with increasingly greater precision. This requirement has meant that magnetic recording heads have been placed increasingly close to the surface of the magnetic disc. The interaction between the magnetic head and the recording surface has become increasingly precise. This requires that every surface of the disc be planarized to a high degree, so that the transducer head, which is flying over the surface of the disc, at a spacing of 25 nm can maintain that fly height without crashing into any bumps on the surface of the disc. It is known that the surface of the disc must be textured in order to optimize the magnetic recording performance of the disc. However, such texturing must be highly uniform so that no contact occurs between the transducer and the textured disc surface.
In order to achieve this goal, planetary polishing has been adopted as an effective method to planarize discs. The fundamental problem is that at least two polishing steps are required to reduce a standard Ni—P plated substrate to a super-smooth finish. The first step planarizes the disc to remove plating and grinding defects and the second reduces the high frequency roughness of the disc. These two polishing steps rely on chemical etching and mechanical abrasive action to remove Ni—P from the disc's surface and can be relatively time consuming.
As a result, the cost of consumables for polishing makes up a significant portion of the substrate cost. Additionally two washing steps are required; one between the two polishing steps and the final wash and these also contribute to yield loss and disc cost.
Moreover, the rotational quill action of the polishing pads generates random scratch patterns, which can produce random scratches particularly if a large abrasive particle (particle agglomerate) or foreign material is introduced into the system.
After the polishing steps, a further step called mechanical texturing is required to circumferentially orient the disc's surface to support an-isotropic or oriented recording. Therefore three mechanical “polishing” steps are required to produce a circumferentially textured disc.
Therefore a continuing need exists for a more cost effective approach to planarization of discs.